fpdns is a program that remotely determines DNS server versions.
It does this by sending a series of borderline DNS queries which
are compared against a table of responses and server versions.

False positives or incorrect versions may be reported when trying
to identify a set of servers residing behind a load-balancing
apparatus where the servers are of different implementations, when
a specific implementation behaves like a forwarder, behind a firewall
without statefull inspection or without Application Intelligence.
